Getting error while converting

@Tanushree Debnath this is a Lead Conversion field mapping issue.

The error is specifically saying that Salesforce needs a value for this Account field during conversion: Account.Support_Plan_Expiration_Date__c

To fix it, create a matching custom field on Lead, then map it to the Account field.

Go to: Setup -> Object Manager -> Lead -> Fields & Relationships -> Map Lead Fields

Then map the Lead field to: Account.Support_Plan_Expiration_Date__c

Salesforce’s lead field mapping help explains this process here: (Salesforce)

Also check whether Support_Plan_Expiration_Date__c is marked as required on Account, or required by a validation rule. If it is required, the Lead must have a valid value before conversion, otherwise the Account cannot be created.

There are similar community posts for this same lead conversion mapping error here: (trailhead.salesforce.com)

After mapping the field, update the Lead with the support plan expiration date and try converting again.